Emerging metal oxide semiconductor TFT with an Indium-Gallium-Zinc Oxide (IGZO) Thin Film Transistor (TFT) as a representative is considered as a device with highest potential in next generation of display technology because it has advantages of both polycrystalline silicon TFT and amorphous silicon TFT. In addition, because the IGZO TFT and the amorphous silicon TFT adopt similar device structures and can be prepared at low temperature, a preparation process of the IGZO TFT can be compatible with a production process of the amorphous silicon TFT, that is to say, a Back Channel Etch (BCE) process which is simple in technological process and low in cost can be adopted to fabricate the IGZO TFT.